Over the past 10 years, improvements have been made in the precision manufacture of automatic transmission components. However, the planetary gear-sets and multi-disc/plate couplings of conventional automotive transmissions have undergone little conceptual change since their first introduction in the 1930's.
No-load losses (built-in parasitic losses) in conventional automotive transmissions having three or more planetary gear sets vary between 15,000 and 20,000 watts. Since 70% of all vehicle use requires 20 to 25 hp for highway driving, a parasitic no-load loss of 20,000 watts (at 25 hp) indicates a transmission efficiency of only about 50%. Therefore, although some improvements have been made in automotive transmissions, there has been little improvement in the efficiency of vehicle drive-lines.